U.S. patent application number 15/593421 was filed with the patent office on 2018-01-04 for chemical sensor, and chemical substance detection method and device.
The applicant listed for this patent is Hitachi, Ltd.. Invention is credited to Shirun HO, Norifumi KAMESHIRO, Sanato NAGATA, Hiromasa TAKAHASHI.
Application Number | 20180003663 15/593421 |
Document ID | / |
Family ID | 60806199 |
Filed Date | 2018-01-04 |
United States Patent
Application |
20180003663 |
Kind Code |
A1 |
KAMESHIRO; Norifumi ; et
al. |
January 4, 2018 |
CHEMICAL SENSOR, AND CHEMICAL SUBSTANCE DETECTION METHOD AND
DEVICE
Abstract
There is a provided a chemical sensor that includes a
semiconductor substrate of a first conductivity type, a first
electrode that is formed on a front surface of the semiconductor
substrate, a second electrode that is disposed to face the first
electrode in a vertical direction, a flow path in which a liquid or
a gas can flow between the first electrode and the second
electrode, and a chemical substance capturing portion that is
disposed in at least a partial region between the first electrode
and the second electrode in the flow path, and bonded with a
predetermined chemical substance, and in which a distance between
the first electrode and the second electrode is set to be 2 nm or
more and 200 nm or less, and a change in dielectric constant
between the first electrode and the second electrode is
detected.
Inventors: |
KAMESHIRO; Norifumi; (Tokyo,
JP) ; TAKAHASHI; Hiromasa; (Tokyo, JP) ;
NAGATA; Sanato; (Tokyo, JP) ; HO; Shirun;
(Tokyo, JP) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
Hitachi, Ltd. |
Tokyo |
|
JP |
|
|
Family ID: |
60806199 |
Appl. No.: |
15/593421 |
Filed: |
May 12, 2017 |
Current U.S.
Class: |
1/1 |
Current CPC
Class: |
H01L 29/2003 20130101;
H01L 29/161 20130101; G01N 27/227 20130101; G01N 33/54393 20130101;
G01N 27/226 20130101; G01N 33/5438 20130101; H01L 29/1608
20130101 |
International
Class: |
G01N 27/22 20060101
G01N027/22; H01L 29/16 20060101 H01L029/16; G01N 33/543 20060101
G01N033/543; H01L 29/20 20060101 H01L029/20; H01L 29/161 20060101
H01L029/161 |
Foreign Application Data
Date |
Code |
Application Number |
Jun 29, 2016 |
JP |
2016-128640 |
Claims
1. A chemical sensor comprising: a semiconductor substrate of a
first conductivity type; a first electrode that is formed on a
front surface of the semiconductor substrate; a second electrode
that is disposed to face the first electrode in a vertical
direction; a flow path in which a liquid or a gas can flow between
the first electrode and the second electrode; and a chemical
substance capturing portion that is disposed in at least a partial
region between the first electrode and the second electrode in the
flow path, and bonded with a predetermined chemical substance,
wherein a distance between the first electrode and the second
electrode is set to be 2 nm or more and 200 nm or less, and a
change in dielectric constant between the first electrode and the
second electrode is detected.
2. The chemical sensor according to claim 1, wherein the first
electrode is configured as a common electrode, the second electrode
is configured as a plurality of second electrodes that are formed
apart from each other, the first electrode is set to be a first
potential, and the plurality of second electrodes are set to be
second potentials, and an electrostatic capacitance between the
first electrode and the plurality of second electrodes is
detected.
3. The chemical sensor according to claim 1, wherein the first
electrode is configured as a plurality of first electrodes on the
front surface of the semiconductor substrate, the second electrode
is configured as a plurality of the second electrodes that are
disposed to face the plurality of the first electrode in the
vertical direction, the plurality of the first electrodes are set
to be the first potentials, the plurality of the second electrodes
are set to be the second potentials, and the electrostatic
capacitances between the plurality of first electrodes and the
plurality of second electrodes are detected.
4. The chemical sensor according to claim 1, further comprising: a
third electrode that is disposed to face the second electrode in a
vertical direction in a direction opposite to a direction in which
the first electrode is disposed with respect to the second
electrode, wherein a distance between the second electrode and the
third electrode is set to be 2 nm or more and 200 nm or less, and
the third electrode is wired so as to be a voltage equal to that of
the first electrode.
5. The chemical sensor according to claim 1, wherein the
semiconductor substrate is formed of a material selected from
silicon, silicon carbide, gallium nitride, gallium arsenide,
germanium, and silicon germanium, and the first electrode is formed
of a semiconductor layer of a second conductivity type that is
formed on the front surface of the semiconductor substrate or an
alloy of at least a portion of the semiconductor substrate and a
metal.
6. The chemical sensor according to claim 5, wherein the second
electrode is formed of a material selected from monocrystalline
silicon, polycrystalline silicon, silicide, nickel, and gold, and
the chemical substance capturing portion is at least one selected
from silicon nitride, tantalum pentoxide, a silane coupling agent,
thiol, and a synthetic molecule prepared by molecular
imprinting.
7. The chemical sensor according to claim 1, wherein the flow path
introduces the chemical substance between the first electrode and
the second electrode in a direction perpendicular to the
semiconductor substrate, passes the chemical substance through
between the first electrode and the second electrode, and
discharges the chemical substance from between the first electrode
and the second electrode in the direction perpendicular to the
semiconductor substrate.
8. The chemical sensor according to claim 1, wherein the first
electrode is configured as a plurality of first electrodes that
includes a first electrode A and a first electrode B on the front
surface of the semiconductor substrate, the second electrode is
configured as a plurality of second electrodes that includes a
second electrode A and a second electrode B which are disposed to
face the plurality of first electrodes in the vertical direction, a
first chemical substance capturing portion is formed on at least a
portion of the first electrode, a second chemical substance
capturing portion is formed on at least a portion of the second
electrode, the first electrode A and the second electrode A face
each other, and a facing area between the electrodes thereof is an
area A, the first electrode B and the second electrode B face each
other, and a facing area between the electrodes thereof is an area
B, the first chemical substance capturing portion and the second
chemical substance capturing portion capture different substances,
and the area A and area B are different from each other.
9. The chemical sensor according to claim 1, wherein the distance
between the first electrode and the second electrode is 10 nm or
less.
10. A chemical substance detection method comprising: using a
semiconductor substrate; using a first electrode that is formed on
a front surface of the semiconductor substrate; using a second
electrode that is disposed to face the first electrode in a
vertical direction; using a chemical substance capturing portion
that is disposed in at least a partial region between the first
electrode and the second electrode, and bonded with a predetermined
chemical substance; setting a distance between the first electrode
and the second electrode to be 100 times or less the size of the
chemical substance; supplying a gas or a liquid containing the
chemical substance, between the first electrode and the second
electrode; detecting a change in dielectric constant between the
first electrode and the second electrode by capturing the chemical
substance in the chemical substance capturing portion; and
detecting the chemical substance based on the change in the
dielectric constant.
11. The chemical substance detection method according to claim 10,
wherein the first electrode, the second electrode, and a flow path
for supplying a gas or a liquid containing the chemical substance
are prepared by a semiconductor manufacturing process.
12. The chemical substance detection method according to claim 11,
wherein a distance between the first electrode and the second
electrode is set to be 2 nm or more and 200 nm or less.
13. A chemical substance detection device comprising: a plurality
of chemical sensors, each of which includes a semiconductor
substrate; a first electrode that is formed on a front surface of
the semiconductor substrate; a second electrode that is disposed to
face the first electrode in a vertical direction; a flow path in
which a liquid or a gas can flow between the first electrode and
the second electrode; a chemical substance capturing portion that
is disposed in at least a partial region between the first
electrode and the second electrode in the flow path, and bonded
with a predetermined chemical substance; and in which a distance
between the first electrode and the second electrode is set to be 2
nm or more and 200 nm or less, wherein one electrode of the first
or second electrode of the chemical sensor is connected to ground,
the other electrode of the chemical sensor is connected to a
detection system, and the detection system includes a power supply
for applying a voltage and a current meter, and detects an
electrostatic capacitance between the first electrode and the
second electrode.
14. The chemical substance detection device according to claim 13,
wherein at least two types or more of different chemical sensors of
the chemical substance capturing portion are included, and each
chemical sensor having the different chemical substance capturing
portion has a different electrode size.
15. The chemical substance detection device according to claim 14,
wherein a plurality of the other electrodes are connected to the
same detection system via selection switches, and only the
information on the chemical sensor that is selected by the
selection switch is selectively output.
Description
CLAIM OF PRIORITY
[0001] The present application claims priority from Japanese
application serial no. JP 2016-128640, filed on Jun. 29, 2016, the
content of which is hereby incorporated by reference into this
application.
BACKGROUND OF THE INVENTION
Field of the Invention
[0002] The present invention relates to a chemical sensor using a
semiconductor substrate, a manufacturing method thereof, and
chemical substance detection device and method.
Background Art
[0003] There are JP-A-2010-160151 and JP-A-2008-111854 as
background art of the field of the invention. In JP-A-2010-160151,
a chemical sensor that uses an antibody probe on an electrode
formed on a nonconductive substrate to detect a presence or absence
of an antigen by an electric sensing method is described. A
conductivity promoting molecule that promotes the conductivity of
the electric sensing method is disposed on the electrode and an
antibody layer is disposed therethrough. Therefore, it is possible
to amplify the signals of the electric sensing type sensor.
[0004] In addition, in JP-A-2008-111854, as a molecular recognition
sensor formed on a semiconductor substrate, a sensor that detects a
change in electrostatic capacitance of a substrate when a
recognition target molecule is captured by a recognition material
portion by using a change in photocurrent is described.
SUMMARY OF THE INVENTION
[0005] A chemical sensor that detects a specific chemical substance
is configured to include a detection unit that detects a chemical
substance and an output unit that outputs a result thereof. A
signal outputted when a trace amount of chemical substance is
detected by the detection unit is small and buried in a noise
signal, and is erroneously detected in some cases.
[0006] For example, as a method for improving erroneous detection
due to the above-described minute signal, there are techniques
described in JP-A-2010-160151 and JP-A-2008-111854. In the sensor
disclosed in JP-A-2010-160151, conductivity between electrodes can
be improved by using the conductivity promoting molecule, and a
signal can be amplified to a level measurable by a measuring
instrument. In addition, in the sensor disclosed in
JP-A-2008-111854, a minute detection signal is amplified by
detecting a photocurrent generated by light irradiation.
[0007] However, in order to amplify the signal, it is necessary to
add a configuration and complicate the structure, which leads to an
increase in a size and a cost of the device. Therefore, it is
necessary to study a chemical sensor which does not require signal
amplification and does not cause erroneous detection.
[0008] According to an aspect of the invention for solving the
above-described problems, there is provided a chemical sensor that
includes a semiconductor substrate of a first conductivity type, a
first electrode that is formed on a front surface of the
semiconductor substrate, a second electrode that is disposed to
face the first electrode in a vertical direction, a flow path in
which a liquid or a gas can flow between the first electrode and
the second electrode, and a chemical substance capturing portion
that is disposed in at least a partial region between the first
electrode and the second electrode in the flow path, and bonded
with a predetermined chemical substance, and in which a distance
between the first electrode and the second electrode is set to be 2
nm or more and 200 nm or less, and a change in dielectric constant
between the first electrode and the second electrode is
detected.
[0009] According to another aspect of the invention, there is
provided a chemical substance detection method that includes using
a semiconductor substrate, a first electrode that is formed on a
front surface of the semiconductor substrate, a second electrode
that is disposed to face the first electrode in a vertical
direction, and a chemical substance capturing portion that is
disposed in at least a partial region between the first electrode
and the second electrode and bonded with a predetermined chemical
substance, setting a distance between the first electrode and the
second electrode to be 100 times or less the size of the chemical
substance, supplying a gas or a liquid containing the chemical
substance between the first electrode and the second electrode,
detecting a change in dielectric constant between the first
electrode and the second electrode by capturing the chemical
substance in the chemical substance capturing portion, and
detecting the chemical substance based on the change in the
dielectric constant.
[0010] According to another aspect of the invention, there is
provided a chemical substance detection device that includes a
plurality of chemical sensors, each of which includes a
semiconductor substrate, a first electrode that is formed on a
front surface of the semiconductor substrate, a second electrode
that is disposed to face the first electrode in a vertical
direction, a flow path in which a liquid or a gas can flow between
the first electrode and the second electrode, a chemical substance
capturing portion that is disposed in at least a partial region
between the first electrode and the second electrode in the flow
path, and bonded with a predetermined chemical substance, and in
which a distance between the first electrode and the second
electrode is set to be 2 nm or more and 200 nm or less, and in
which one electrode of the first or second electrode of the
chemical sensor is connected to ground, the other electrode of the
chemical sensor is connected to a detection system, and the
detection system includes a power supply for applying a voltage and
a current meter, and detects an electrostatic capacitance between
the first electrode and the second electrode.
[0011] The chemical sensor according to the invention can detect
the change in the dielectric constant between facing electrodes
without requiring signal amplification. The problems,
configurations, and effects other than those described above will
be clarified by the description of the embodiments below.
BRIEF DESCRIPTION OF THE DRAWINGS
[0012] FIGS. 1A and 1B are conceptual diagrams illustrating a main
part of a chemical sensor according to Example 1.
[0013] FIG. 2A is a cross-sectional view of the main part
illustrating a manufacturing process of the chemical sensor
according to Example 1.
[0014] FIG. 2B is a cross-sectional view of the main part
illustrating the manufacturing process of the chemical sensor
according to Example 1 (continued).
[0015] FIG. 2C is a cross-sectional view of the main part
illustrating the manufacturing process of the chemical sensor
according to Example 1 (continued).
[0016] FIG. 2D is a cross-sectional view of the main part
illustrating the manufacturing process of the chemical sensor
according to Example 1 (continued).
[0017] FIG. 2E is a cross-sectional view of the main part
illustrating the manufacturing process of the chemical sensor
according to Example 1 (continued).
[0018] FIG. 3A is a cross-sectional view of a main part
illustrating a structure of the chemical sensor according to
Example 1.
[0019] FIG. 3B is a plan view of the main part illustrating the
structure of the chemical sensor according to Example 1.
[0020] FIG. 3C is a cross-sectional view of the main part
illustrating the structure of the chemical sensor according to
Example 1.
[0021] FIG. 4 is a cross-sectional view of a main part illustrating
another modification example of a structure of the chemical sensor
according to Example 1.
[0022] FIG. 5 is a cross-sectional view of a main part illustrating
another modification example of the structure of the chemical
sensor according to Example 1.
[0023] FIGS. 6A and 6B are cross-sectional views of main parts
illustrating still another modification example of the structure of
the chemical sensor according to Example 1.
[0024] FIG. 7 is a cross-sectional view of a main part illustrating
still another modification example of the structure of the chemical
sensor according to Example 1.
[0025] FIG. 8 is a cross-sectional view of a main part illustrating
still another modification example of the structure of the chemical
sensor according to Example 1.
[0026] FIG. 9 is a cross-sectional view of a main part illustrating
still another modification example of the structure of the chemical
sensor according to Example 1.
[0027] FIG. 10 is a cross-sectional view of a main part
illustrating still another modification example of the structure of
the chemical sensor according to Example 1.
[0028] FIG. 11A is a cross-sectional view of a main part
illustrating a manufacturing process of a chemical sensor according
to Example 3.
[0029] FIG. 11B is a cross-sectional view of the main part
illustrating the manufacturing process of the chemical sensor
according to Example 3 (continued).
[0030] FIG. 12 is a schematic diagram illustrating a configuration
of a chemical substance detection device according to Example
4.
[0031] FIG. 13 is a schematic diagram illustrating another
modification example of the configuration of the chemical substance
detection device according to Example 4.
[0032] FIG. 14 is a schematic diagram illustrating another
modification example of the configuration of the chemical substance
detection device according to Example 4.
DETAILED DESCRIPTION OF THE INVENTION
[0033] In the following embodiments, when necessary for
convenience, the description will be divided into a plurality of
sections or embodiments, but these are not unrelated to each other,
and one is related to a modification example, detail, and a
supplementary explanation of a portion or all of the other, except
for a case of being expressly stated in particular.
[0034] In addition, in the following embodiments, when the number
of elements (including number, numerical value, amount, range, and
the like) is referred to, the number of elements is not limited to
a specific number thereof, and may be the specific number or more
or less, except for a case of being expressly stated in particular
and a case of being obviously limited to the specific number in
principle.
[0035] In addition, in the following embodiments, it is needless to
say that the configuration elements thereof (including element step
and the like) are not necessarily indispensable, except for a case
of being expressly stated in particular and a case where it is
obviously considered indispensable in principle.
[0036] In addition, when "comprising A", "consisting of A", "having
A", and "including A" are referred to, it is needless to say that
these do not exclude other elements, except for a case where only
the element thereof is expressly stated in particular. Similarly,
in the following embodiments, when a shape and a positional
relation of configuration elements are referred to, these include
substantially similar or similar to the shape thereof, except for a
case of being expressly stated in particular and a case where it is
obviously considered not to be so in principle. This fact is
similar to the above numerical values and ranges.
[0037] In addition, in all the drawings for explaining the
following embodiments, those having the same functions are denoted
by the same reference numerals in principle, and the repeated
descriptions thereof will be omitted. Hereinafter, the embodiment
will be described in detail with reference to the drawings.
[0038] A chemical sensor for detecting a specific chemical
substance is configured to include a detection unit for detecting
the chemical substance and an output unit for outputting the result
thereof. In order to output a signal change when a trace amount of
chemical substance is detected in the detection unit, signal
amplification is required in the output unit. However, in order to
amplify the signal, there is a problem that it is necessary to add
a configuration and complicate a structure, which leads to an
increase in a size and a cost of the device. Therefore,
consideration of the chemical sensor that does not require the
signal amplification and that does not cause erroneous detection is
required. In the chemical sensor of an example described below,
when detecting a trace amount of the chemical substance in the
detection unit, a change rate of the signal is increased, and the
structure is such that signal amplification is not required.
[0039] An example of a chemical sensor includes a first electrode
that is formed on a front surface of the semiconductor substrate, a
second electrode that is disposed to face the first electrode in a
vertical direction, a flow path in which a liquid or a gas can flow
between the first electrode and the second electrode, and a
chemical substance capturing portion that is disposed in at least a
partial region between the first electrode and the second electrode
in the flow path, and has high bonding property with a
predetermined chemical substance, and in which a distance between
the first electrode and the second electrode is smaller than a
predetermined ratio with respect to a size of a molecule of the
predetermined chemical substance, and a change in dielectric
constant between the first electrode and the second electrode is
detected when the predetermined chemical substance is bonded to the
chemical substance capturing portion.
Example 1
[0040] Structure of Chemical Sensor
[0041] The structure of the chemical sensor according to Example 1
will be described with reference to FIGS. 1A and 1B. FIGS. 1A and
1B are conceptual diagrams illustrating the structure of the
chemical sensor according to Example 1. As illustrated in the
sectional shape in FIG. 1A, in a chemical sensor 10 according to
Example 1, a first electrode 2 which is an n.sup.+-type
semiconductor region formed by an impurity implantation of high
concentration on the front surface of a semiconductor substrate 1
of p-type silicon (Si), a second electrode 3 formed of n.sup.+
polycrystalline silicon disposed to face the first electrode 2 in a
vertical direction, and a flow path 4 for flowing a liquid or a gas
between the first electrode 2 and the second electrode 3 is formed.
A chemical substance capturing portion 5 having a high bonding
property with a predetermined chemical substance 6 is formed in at
least a portion of the first electrode 2 and the second electrode 3
in the flow path.
[0042] The chemical substance capturing portion 5 is a silane
coupling agent having an organic functional group on the front
surface, or a synthetic molecule prepared by further molecular
imprinting on the front surface of the silane coupling agent, or a
modified antibody. A distance D between the first electrode 2 and
the second electrode 3 is set to be a value smaller than a
predetermined ratio (approximately 100 times) with respect to the
size of the molecule of the predetermined chemical substance 6 to
be detected. Furthermore, the first electrode 2 and the second
electrode 3 are connected to a detection system 12 including a
power supply.
[0043] A connection relationship between a main part of the
chemical sensor 10 and a detection system including the power
supply will be described with reference to FIG. 1A. As illustrated
in FIG. 1A, the first electrode 2 and the second electrode 3 are
connected to the detection system 12 including the power supply via
a metal wiring layer (not illustrated) or the like. The detection
system 12 detects a change in capacitance between the first
electrode 2 and the second electrode 3. As a specific
configuration, a measurement method used for capacitance
measurement of an ordinary capacitor may be used, and may be
selected according to characteristics of the object to be
evaluated, such as (1) measuring the current at the time using a
low frequency voltage that can pass through the capacitance, (2)
measuring a current change at the time by applying a small
potential difference, (3) measuring the change in the voltage at
the time by applying a current pulse, and (4) measuring the current
change by superimposing the DC voltage on the AC voltage. In
addition, dependency on the frequency of the AC voltage is measured
as required in some cases.
[0044] The capacitance is derived from an equation of impedance
Z
V=ZI
Z=R+jwL+1/(jwC)
[0045] (R is a resistance, j is an imaginary unit, L is an
inductance, C is a capacitance, w=2.pi.f is an AC angular frequency
of a frequency f, V is a voltage measured by a voltage meter, and I
is a current measured by a current meter). A detection principle of
the example is basically to detect the change of C in the equation
of impedance Z with R and L fixed.
[0046] The capacitance C between plate electrodes is applied by
C=.di-elect cons.S/D (.di-elect cons. is a dielectric constant of
the substances between the electrodes and S is an area of the plate
electrode).
[0047] In the example, the distance D is set to be a value smaller
than approximately 100 times the size of the molecule of the
predetermined chemical substance 6 to be detected. In this manner,
the proportion of the chemical substance occupying the space
between the electrodes increases, so that the dielectric constant
between the electrodes greatly changes by the chemical substance 6
captured in the chemical substance capturing portion 5. As a
result, the rate of change of .di-elect cons. increases and a large
change rate of C is obtained.
[0048] FIG. 1B is an equivalent circuit diagram in which the
chemical sensor 10 of FIG. 1A is rewritten with a simplified
symbol. CS in the figure is an abbreviation for the chemical
sensor.
[0049] "-" and "+" are symbols indicating relative impurity
concentrations of n-type or p-type conductivity, for example, the
impurity concentration of the n-type impurity increases in the
order of "n.sup.-", and "n.sup.+", and the impurity concentration
of the p-type impurity increases in the order of "p.sup.-", "p",
and "p.sup.+".
[0050] Manufacturing Process of Chemical Sensor
[0051] In the chemical sensor 10 having the configuration
illustrated in FIGS. 1A and 1B, since the rate of change in the
capacitance between the first electrode 2 and the second electrode
3 caused by the chemical substance 6 is large, detection with high
sensitivity becomes possible. Such a configuration can be
manufactured by a semiconductor process to which a semiconductor
technology is applied. A manufacturing method of the chemical
sensor according to Example 1 will be described in order of
processes with reference to FIGS. 2A to 2E. Each figure is a
cross-sectional view of the main part illustrating a manufacturing
process of the chemical sensor according to Example 1.
[0052] In a process of FIG. 2A, the semiconductor substrate 1 of
p-type Si is first prepared. The Si semiconductor substrate 1 has
different specifications of various surface orientations and
resistivity, but any specifications do not matter as long as the
specifications can be used for ordinary semiconductor process
applications.
[0053] Next, a mask material 14 is formed on the upper surface of
the p-type Si semiconductor substrate 1, and the mask material 14
is patterned by a photolithography technique. Any other materials
can be used as the mask material as long as the material is to be
the mask at the time of ion implantation, for example, such as
silicon oxide (SiO.sub.2), silicon nitride (Si.sub.3N.sub.4),
resist material or the like formed by chemical vapor deposition
(CVD) method.
[0054] Subsequently, an n-type impurity 200 is ion-implanted into
the upper surface of the p-type Si semiconductor substrate 1
exposed from the patterned mask material 14, so that an
n.sup.+-type semiconductor region 15 is formed on the upper surface
of the p-type Si semiconductor substrate 1. For an ion implantation
condition, for example, phosphorus (P) is set in the range of 3 to
50 keV and 1 to 5.times.10.sup.15 cm.sup.-2.
[0055] After removal of the mask material 14, an activation process
(annealing) of implanted impurity is performed, so that the
n.sup.+-type semiconductor region 15 becomes the first electrode 2.
The ion implantation condition is adjusted so that the impurity
concentration at this time is approximately 1 to 5.times.10.sup.20
cm.sup.-3.
[0056] FIG. 2B illustrates a process after forming the first
electrode 2. A spacer 16 is formed on the upper surface of the
p-type Si semiconductor substrate 1. The material of the spacer may
be any material which is selectively etched with hydrofluoric acid,
for example, SiO.sub.2 formed by a CVD method.
[0057] After forming the spacer 16, a film serving as a material of
the second electrode, for example, n.sup.+ polycrystalline silicon
by the CVD method is formed on the entire upper surface of the
spacer 16, the mask material 14 is formed on the upper surface
thereof, and the mask material 14 is patterned by a
photolithography technique. Thereafter, a layer serving as the
material of the second electrode is processed to form the second
electrode 3.
[0058] FIG. 2C illustrates a process after forming the second
electrode 3 by removing the mask material 14. The exposed spacer 16
is selectively etched with hydrofluoric acid to form the flow path
4 between the electrodes.
[0059] FIG. 2D illustrates a process after forming the flow path 4
between the electrodes. A protective film 20 is formed on the
second electrode 3 and the semiconductor substrate 1. As the
protective film 20, in order to prevent the film from flowing and
accumulating in the flow path 4 between the formed electrodes, for
example, a physical vapor deposition (PVD), or SiO.sub.2 or
Si.sub.3N.sub.4 formed by the CVD method using a condition with
poor step coverage is used.
[0060] FIG. 2E illustrates a process after forming the protective
film 20. The protective film 20 is etched so as to leave the upper
portions of the second electrode 3 and the second electrode 3. The
space on the side of the second electrode 3 and the protective film
20 removed by etching functions as the flow path 4 of a medium for
transporting the chemical substance. Although not illustrated in
the drawing, a partition wall for restricting the flow path by
leaving a portion of the protective film 20 can be provided.
[0061] Thereafter, after the chemical substance capturing portion 5
is formed on a side wall of the flow path including the front
surfaces of the first electrode 2 and the second electrode 3, the
chemical substance capturing portion 5 at an unnecessary place is
removed as required.
[0062] FIGS. 3A to 3C are schematic views of the chemical sensor 10
completed by the process of FIGS. 2A to 2E. FIG. 3A is a
cross-sectional view after completing the process of FIG. 2E. The
gas or liquid carrying the chemical substance 6 is transported, for
example, as illustrated by an arrow in FIGS. 3A to 3C, and the
chemical substance 6 is captured by the chemical substance
capturing portion 5 between the electrodes.
[0063] FIG. 3B is a top view of the configuration of FIG. 3A. The
cross-sectional view of FIG. 3A illustrates a cross section A-A of
FIG. 3B. In order to form the flow path 4, a lower part of the
second electrode 3 of the chemical sensor 10 illustrated in FIG. 3B
is a gap obtained by removing the spacer 16. For the description,
the protective film 20 is omitted from illustration.
[0064] In the example, in order to hold the second electrode 3, a
columnar structure 17 is disposed at a predetermined position. In
the example of FIG. 3B, the second electrode 3 is formed around the
columnar structure 17, and the hidden invisible chemical substance
capturing portion 5 and the first electrode 2 have the same planar
shape as the second electrode 3.
[0065] In addition, FIG. 3B schematically illustrates an inlet 4in
and an outlet 4out of the flow path 4. The flow path 4 in the
direction perpendicular to the semiconductor substrate 1 is formed
by removing the protective film 20 up to the semiconductor
substrate 1 by the process of FIG. 2E. The shape and size of the
flow path 4 in the vertical direction can be arbitrarily formed by
etching of the protective film 20 in FIG. 2D. In the drawing, the
inlet 4in and the outlet 4out are illustrated relatively small, but
it is generally preferable to form as large as possible and leave
necessary portion such as partition wall of the flow path.
[0066] In the configuration of FIGS. 3A to 3C, the number of the
columnar structures 17 is two, but three or more columnar
structures 17 may be provided by extending the sensor portion such
as the second electrode 3 further in a B-B direction.
[0067] FIG. 3C illustrates a cross section B-B of FIG. 3B. As a
material of the columnar structure 17, it is necessary to be a
material resistant to etching when the spacer 16 is removed. For
example, the material is an insulator which is hardly etched with
hydrofluoric acid, and uses, for example, silicon nitride
(Si.sub.3N.sub.4) or tantalum pentoxide (Ta.sub.2O.sub.5). Although
the process is not limited, it may be formed after forming the film
to be the material of the second electrode, and before removing the
spacer 16. For example, after removing the mask material 14 in the
state of FIG. 2B, a hole penetrating the second electrode 3 and the
spacer 16 to reach the first electrode 2 or the semiconductor
substrate 1 is formed, and an insulator is accumulated in the hole.
The columnar structure 17 is formed, so that a mechanical strength
of the second electrode 3 can be improved.
[0068] Modification Example of Chemical Sensor and Manufacturing
Method of Chemical Sensor
[0069] Next, a modification example of the chemical sensor
according to Example 1 and a manufacturing method of the chemical
sensor will be described.
[0070] (1) In the example of FIGS. 3A to 3C, the chemical sensor
configured to include a pair of first electrode and second
electrode disposed to face each other is used, but the chemical
sensor configured to include a plurality of pairs of first
electrode and second electrode may be used.
[0071] FIG. 4 is a cross-sectional view illustrating a structure of
a main part of the chemical sensor 10 using the first electrode 2
as a common electrode, which is configured to include two pairs of
first electrodes 2 and second electrodes 3 and 3'. A partition wall
18 partitioning the flow path 4 is configured by leaving the
protective film 20 by etching. Although the mechanical strength can
be improved and the flow of the sample can be adjusted by the
partition wall, the partition wall can be omitted in the example
illustrated in FIG. 4 and the followings. In a case where equal
samples are simultaneously supplied to the plurality of chemical
sensors 10, it may be preferable that there is no partition wall
18. In addition, although not illustrated in the drawings, both the
left and right sides of the chemical sensor 10 can be configured
similarly to the partition wall 18.
[0072] As illustrated in FIG. 4, the first electrode 2 is formed on
the front surface of the semiconductor substrate 1, and serves as
the common electrode. Two pairs of second electrodes 3 and 3' are
disposed to face the common first electrode 2. The two pairs of
sensor elements configured to include the common first electrode 2
and the second electrodes 3 and 3' are respectively provided with
the flow paths 4 and 4' and the chemical substance capturing
portions 5 and 5' with the same type. Since the second electrodes 3
and 3' are connected to a common terminal via the metal wiring
layer, one chemical sensor 10 is configured by parallel connection
of two pairs of sensor elements. In the example of FIG. 4, the
capacitances are connected in parallel, so that the capacitance to
be detected can be increased.
[0073] FIG. 5 is another example, and a cross-sectional view
illustrating a structure of a main part of the chemical sensor 10
having two pairs of first electrodes 2 and 2', second electrodes 3
and 3', the flow path 4, and the chemical substance capturing
portions 5 and 5' on the common semiconductor substrate 1.
[0074] As illustrated in FIG. 5, two pairs of first electrodes 2
and 2' are separately formed on the common semiconductor substrate
1, and second electrodes 3 and 3' corresponding thereto, flow paths
4 and 4', and chemical substance capturing portions 5 and 5' with
the same type may be configured to be provided. In this case as
well, as in FIG. 4, since the second electrodes 3 and 3' are
connected to the common terminal via the metal wiring layer, one
chemical sensor 10 is configured by parallel connection of two
pairs of sensor elements. Therefore, as in the example of FIG. 4,
the capacity to be detected can be increased.
[0075] In the configuration of FIG. 5, a patterning process for
separately forming the first electrodes 2 and 2' is added, but
since the first electrodes 2 and 2' are formed only in regions
facing the second electrodes 3 and 3', unnecessary parasitic
capacitance can be suppressed, and a structure suitable for
electrostatic capacitance design of the chemical sensor 10 is
obtained.
[0076] (2) In Example 1, the chemical sensor is configured to
include the first electrode and the second electrode which are
disposed to face each other, but a chemical sensor with a
configuration having a third electrode set to the same potential as
the first electrode may be used.
[0077] FIG. 6A illustrates an example of a chemical sensor 10 in
which a first electrode 2 formed on a p-type Si semiconductor
substrate 1, a second electrode 3 disposed so as to face the first
electrode 2, and a third electrode 7 disposed so as to face the
second electrode on the side opposite to the direction in which the
first electrode is disposed with respect to the second electrode
are provided. The chemical sensor 10 may have a configuration in
which the third electrode 7 is formed, for example, to include
n.sup.+-polycrystalline silicon by the CVD method, and patterned,
and the flow path 4 and the chemical substance capturing portion 5
are provided.
[0078] Here, it is configured that the liquid or gas can
respectively flow in between the flow path 4, the first electrode 2
and the second electrode 3, and between the second electrode 3 and
the third electrode 7. In addition, the chemical substance
capturing portion 5 is formed not only in the first electrode 2 and
the second electrode 3 but also in the third electrode 7.
Furthermore, the third electrode 7 is connected to the first
electrode 2 and the common terminal via the metal wiring layer.
Therefore, one chemical sensor 10 is configured by parallel
connection of two pairs of sensor elements disposed one above the
other, and it is configured to increase the electrostatic
capacitance of the chemical sensor.
[0079] In the example of FIGS. 6A and 6B, both the distance between
the first electrode 2 and the second electrode 3, and the distance
between the second electrode 3 and the third electrode 7 are set to
be a value smaller than approximately 100 times the size of the
chemical substance 6 molecules. The chemical substance capturing
portions 5 are provided on both of the facing electrodes in the
above-described example, but may be provided on only one thereof.
As a matter of course, the sensitivity improves when the units are
provided on both.
[0080] FIG. 6B is an equivalent circuit diagram in which the
chemical sensor 10 of FIG. 6A is rewritten with a simplified
symbol.
[0081] FIG. 7 illustrates an example of a chemical sensor having a
combination of the above (1) and (2). In other words, the chemical
sensor 10 is configured to include a plurality of pairs of the
first electrode 2, the second electrode 3, and the third electrode
7. In this configuration, since the effects of increasing the
individual electrostatic capacitances described above are obtained
by combining, a chemical sensor having a larger electrostatic
capacitance in the same area can be obtained.
[0082] (3) In addition, in Example 1, although the semiconductor
substrate 1 is set to be a p-type Si, without being limited
thereto, an n-type Si, an n-type silicon carbide (SiC), or a p-type
SiC may be used. However, in a case where the conductivity type of
the substrate is the n-type, from the viewpoint of element
isolation and reduction of parasitic capacitance, it is preferable
to form a semiconductor region 15 by p-type ion implantation.
[0083] (4) In addition, although the n.sup.+-type semiconductor
region 15 formed by ion-implanting an n-type impurity into the
upper surface of the p-type Si semiconductor substrate 1, and
performing the activation process of the implanted impurity
(annealing) is used as the first electrode 2 in Example 1, the
example is not limited thereto. For example, a silicide layer
formed by reacting at least a portion of the n.sup.+-type
semiconductor region 15 with a metal may be used as the first
electrode 2.
[0084] FIG. 8 is a cross-sectional view illustrating a structure of
a main part of the chemical sensor in which the n.sup.+-type
semiconductor region 15 is partially silicided to form the first
electrode 2. Here, a metal for forming the silicide layer may be a
metal material such as nickel, titanium, tungsten, which is
generally used in the semiconductor manufacturing process.
[0085] (5) In addition, although the n.sup.+ polycrystalline
silicon is used as the second electrode 3 in Example 1, the example
is not limited thereto. For example, by using a silicon on
insulator (SOI) substrate for the semiconductor substrate,
monocrystallin silicon can be used as the second electrode 3. In
addition, the silicide layer formed by siliciding polycrystalline
silicon or monocrystallin silicon as described above may be used as
the second electrode 3. Furthermore, a metal which does not
disappear when the spacer is removed by etching, and which is not
etched with hydrofluoric acid or has a slow etching rate, such as
nickel or gold may be used as the second electrode 3.
[0086] (6) In addition, although the third electrode 7 is formed to
include, for example, the n.sup.+ polycrystalline silicon by the
CVD method in the above-described (2) of Example 1, the example is
not limited thereto. For example, a silicide layer, or nickel or
gold which is a metal not etched with hydrofluoric acid or having a
slow etching rate may be used as the third electrode 7.
[0087] (7) In addition, although the p-type Si is used in the
semiconductor substrate 1, the n.sup.+ semiconductor region is used
in the first electrode 2, the n.sup.+ polycrystalline silicon is
used in the second electrode 3, and the n.sup.+ polycrystalline
silicon is used in the third electrode 7 in the above-described (2)
of Example 1, the example is not limited thereto. For example,
n-type Si, n-type SiC or p-type SiC may be used in the
semiconductor substrate, n.sup.+ and p.sup.+ semiconductor regions
or silicide formed by ion-implanting may be used in the first
electrode 2, nickel or gold which is the metal not etched with
hydrofluoric acid or having the slow etching rate may be used in
the second electrode 3, and n.sup.+ and p.sup.+ polycrystalline
silicon or silicide maybe used in the third electrode 7,
respectively.
[0088] (8) In addition, as illustrated in FIGS. 4 and 5, although
two pairs (plural) of sensor elements are formed on the common
semiconductor substrate 1 in the above-described (1) of Example 1,
and one chemical sensor 10 is configured by parallel connection of
the two pairs of sensor elements, the example is not limited
thereto.
[0089] As illustrated in FIG. 9, the example may be two pairs of
chemical sensors 10 and 10' configured to include two pairs of
first electrodes 2 and 2' which are separately formed on the common
semiconductor substrate 1, the second electrodes 3 and 3'
corresponding thereto, the flow paths 4 and 4', the chemical
substance capturing portions 5 and 8 with different types, and to
separately measure the electrostatic capacitance. Different
chemical substances 6 and 9 can be detected by mixing chemical
sensors 10 and 10' provided with different chemical substance
capturing portions 5 and 8.
[0090] FIG. 10 illustrates another example. Although the chemical
substance capturing portions 5 and 8 of the chemical sensors 10 and
10' have substantially the same area in the example of FIG. 9, in
order to adjust the signal intensity obtained from the chemical
sensors 10 and 10', and to simplify a gain adjustment in the
measuring circuit, a facing area between the electrodes may be
varied for each chemical sensor and 10' provided with different
chemical substance capturing portions 5 and 8.
Operation and Effect of Example
[0091] Next, the effect according to Example 1 will be described
using FIG. 1A again. As illustrated in FIG. 1A, the predetermined
chemical substance 6 is captured by the chemical substance
capturing portion 5 for a certain period of time and stagnates.
While the prescribed chemical substance 6 is stagnant, the
predetermined chemical substance 6 exists in a form in which the
liquid or gas (for example, air) flowing in the flow path is
partially replaced, and the dielectric constant between the first
electrode 2 and the second electrode 3 which are two facing
electrodes changes. As for the change in the dielectric constant,
the detection signal is measured as a change in the electrostatic
capacitance in the detection system 12 connected via the metal
wiring.
[0092] Here, the intensity of the detection signal is determined by
the size of the chemical substance 6 captured for a certain time by
the chemical substance capturing portion 5, and the distance
between the two facing electrodes. For example, in a case of an
odorant molecule drifting in air, the molecule is a low molecular
weight substance with high volatility, and the molecular weight is
approximately 17 to 400 of ammonia. Therefore, in the case of the
odorant molecule, the molecule is only approximately 0.1 to 2 nm in
size. If the molecule is circular or elliptical, the size is a
value approximated by a long diameter, and if the molecule is a
string or amorphous molecule, the size is a value approximated by a
length or a long side. Depending on the accuracy of the detection
system, in a case of an evaluation system that can measure up to
several fF as a change in minute signal intensity, and in a case
where ammonia is captured on the entire surface of the chemical
substance capturing portion 5 and the air in the region thereof is
entirely replaced by a capacitor having the electrode size of 100
.mu.m.times.100 .mu.m and the distance between the electrodes of 10
nm, a detection signal corresponding to the replaced amount is
obtained. Therefore, the odorant molecule is easily detected by
setting the distance between the electrodes to approximately 100
times or less the size of the molecule to be detected. Therefore,
by setting the distance D between two facing electrodes to 200 nm
or less, more preferably 10 nm or less, even when the target is a
substance having a small molecular weight, various types of odorant
molecules can be detected, without requiring signal
amplification.
[0093] In addition, it is preferable that the distance D between
two facing electrodes ensures a size that functions as a flow path
of the odorant molecule. When the size of the odorant molecule is
approximately 0.1 to 2 nm as described above, the flow path width F
is ensured approximately ten times that of the odor molecule in the
direction perpendicular to the semiconductor substrate 1, and is
ensured approximately 1 to 20 nm. Since the flow path width F is
obtained by subtracting the thickness of the chemical substance
capturing portion 5 from the distance D between the electrodes, if
the thickness of the chemical substance capturing portion 5 is set
to be 1 nm in a single layer, it is preferable to secure at least 2
nm as the distance D between the electrodes. It is possible to
process in units of nm in the current semiconductor process, and
device processing with the dimensions as described above is
possible by applying a semiconductor process.
Example 2
[0094] A structure of a chemical sensor according to Example 2 is
schematically the same as that of Example 1, but the material of
the chemical substance capturing portion 5 and the material of the
electrode depending thereon are different therefrom.
[0095] Points different from Example 1 of the structure of the
chemical sensor 10 according to Example 2 will be described with
reference to FIGS. 1A and 1B. In Example 2, the semiconductor
substrate 1 is set to be a general semiconductor substrate which is
not etched with hydrofluoric acid or has a slow etching rate. As
such a semiconductor substrate, for example, silicon (Si), silicon
carbide (SiC), gallium nitride (GaN), gallium arsenide (GaAs),
germanium (Ge), silicon germanium (SiGe) or the like may be
used.
[0096] The first electrode 2 uses the n.sup.+ and p.sup.+
semiconductor regions formed by ion-implanting, or an alloy of a
semiconductor region and a metal. The second electrode 3 uses a
thiol-modifiable metal such as gold. The chemical substance
capturing portion 5 uses thiol having an organic functional group
on the front surface, or synthesized molecules further produced by
molecular imprinting on the front surface of thiol, or molecules
with modified antibody. Therefore, in a case of an electrode which
cannot be modified with thiol, the chemical substance capturing
portion 5 on the side of the first electrode 2 is not formed.
[0097] A modification example of Example 2 will be described with
reference to FIGS. 6A and 6B. The first electrode 2, the second
electrode 3, and the chemical substance capturing portion 5 are the
same as in Example 1. Furthermore, the third electrode 7 uses, for
example, n.sup.+ polycrystalline silicon by a CVD method, a
silicide layer, and nickel or gold which is a metal not etched with
a hydrofluoric acid or having a slow etching rate. Here, in a case
of an electrode which cannot be modified with thiol as the third
electrode 7, the chemical substance capturing portion 5 on the side
of the third electrode 7 is not formed.
[0098] In Example 2, the material of the chemical substance
capturing portion 5 and the material of the electrode depending
thereon are different, but the effect thereof is obtained in the
same manner as in Example 1. However, since the material of each
portion is different, a more suitable method may be selected from
the easiness in forming the chemical substance capturing portion 5
and easiness in handling the medicine.
Example 3
[0099] A structure of a chemical sensor according to Example 3 is
schematically the same as that of Example 1, but the material of
the chemical substance capturing portion 5 and the material of the
electrode depending thereon are different therefrom.
[0100] Points different from Example 1 of the structure of the
chemical sensor 10 according to Example 3 will be described with
reference to FIGS. 1A and 1B. In Example 3, the semiconductor
substrate 1 may be a general semiconductor substrate which is not
etched with hydrofluoric acid, or has a slow etching rate. The
first electrode 2 uses the n.sup.+ and p.sup.+ semiconductor
regions formed by ion-implanting, or an alloy of a semiconductor
region and a metal. The second electrode 3 uses electrode materials
generally used in semiconductor manufacturing process such as
n.sup.+ polycrystalline silicon by a CVD method, a silicide layer,
and nickel or gold which is a metal not etched with a hydrofluoric
acid or having a slow etching rate. The chemical substance
capturing portion 5 uses silicon nitride (Si.sub.3N.sub.4) or
tantalum pentoxide (Ta.sub.2O.sub.5) which is an insulator not
etched with hydrofluoric acid or having a slow etching rate.
[0101] Points different from Example 1 of the manufacturing method
of the chemical sensor 10 according to Example 3 will be described
with reference to FIGS. 11A and 11B. The manufacturing method of
the chemical sensor according to Example 3 is the same as that of
Example 1 up to the intermediate process, but the manufacturing
method differs from the process after forming the n.sup.+-type
semiconductor region 15 illustrated in FIG. 2A, and after forming
the first electrode 2 by removing the mask material 14.
[0102] As illustrated in FIG. 11A, after forming the first
electrode 2, silicon nitride (Si.sub.3N.sub.4) or tantalum
pentoxide, which is an insulator not etched with hydrofluoric acid
or having a slow etching rate, is formed on the upper surface of
the semiconductor substrate 1, as a chemical substance capturing
portion 5. Next, a spacer 16 is further formed, and the chemical
substance capturing portion 5 is further formed thereon.
[0103] As a subsequent process in FIG. 11B, a film to be the
material of the second electrode, for example, n.sup.+
polycrystalline silicon by the CVD method is formed on the upper
surface of the chemical substance capturing portion 5. A mask
material 14 is formed on the upper surface of the n.sup.+
polycrystalline silicon, the mask material 14 is patterned by a
photolithography technique, and thereafter the layer to be the
material of the second electrode is processed to form a second
electrode 3. Further, the chemical substance capturing portion 5 is
similarly processed.
[0104] Next, the spacer 16 is selectively etched with hydrofluoric
acid to form a flow path 4. Thereafter, if necessary, the chemical
substance capturing portion 5 on the semiconductor substrate 1 is
etched so that the chemical sensor having the shape illustrated in
FIGS. 3A to 3C is substantially completed.
[0105] In Example 3, since the chemical substance capturing portion
5 is previously formed and there is a limit applicable to the
material thereof, it is difficult to form a chemical substance
capturing portion for a certain chemical substance. On the other
hand, since the unit is formed by film formation prior to flow path
formation, a uniform chemical substance capturing portion 5 can be
obtained.
Example 4
[0106] It is possible to configure a chemical substance detection
device by using a plurality of pieces of at least one of the
chemical sensors 10 described in Examples 1 to 3 described
above.
[0107] FIG. 12 is a schematic diagram illustrating a configuration
of a chemical substance detection device 11 according to Example 4.
As illustrated in FIG. 12, a plurality of sets are built as a set
of chemical sensors 10-1 to 10-m and detection systems 12-1 to 12-m
for detecting the signals thereof in the chemical substance
detection device 11. These plural sets are connected to the same
ground line (GND) so as to have a common potential.
[0108] One electrode of the chemical sensor 10 configuring each set
is commonly connected to the ground line, and the other electrode
of the chemical sensor is connected to each detection system 12.
Each detection system 12 is provided with a power supply for
applying a voltage and a current meter, and can detect a chemical
substance by detecting an electrostatic capacitance according to a
dielectric constant between the first electrode and the second
electrode.
[0109] In the chemical substance detection device 11 according to
Example 4, for example, each chemical sensor 10 is spatially widely
disposed, and thus the spatial distribution of a predetermined
chemical substance can be measured.
[0110] In addition, the plurality of chemical sensors 10-1 to 10-m
use the same types of sensors in the example of FIG. 12. As a
modification example of Example 4, it is possible to use different
types of sensors in the plurality of chemical sensors 10-1 to 10-m.
That is, the type of the predetermined chemical substance 6
captured by the chemical substance capturing portion 5 is
different. Therefore, it is possible to simultaneously measure a
plurality of types of chemical substances 6. This principle is the
same as previously described in FIG. 9.
[0111] In addition, in order to adjust signal intensities obtained
from the chemical sensors 10-1 to 10-m, the facing area between the
electrodes may be changed for each chemical sensor 10 provided with
different chemical substance capturing portions 5 as another
modification example of Example 4. This principle is the same as
previously described in FIG. 10.
[0112] A further modification example of Example 4 will be
described with reference to FIG. 13. In FIG. 13, a plurality of
chemical sensors 10-1 to 10-n in which the types of predetermined
chemical substances 6 captured by the chemical substance capturing
portion 5 are different, and the facing areas of the electrodes are
different are connected to the detection system 12 via a selection
switch 13. The selection switch 13 may switch on/off the electrical
connection, and uses, for example, a transistor, micro electro
mechanical systems (MEMS) switch, or the like. In the modification
example of Example 4, since the plurality of chemical sensors 10-1
to 10-n are connected to one detection system 12 via the selection
switch 13, the chemical substance detection device 11 can be
downsized. In addition, the facing areas between the electrodes of
the chemical sensors 10-1 to 10-n are changed, and thus it is easy
to adjust the output level and process in one detection system
12.
[0113] A further modification example of Example 4 will be
described with reference to FIG. 14. In FIG. 14, a plurality of
chemical substance detection devices 11-1 to 11-m in which a
plurality of chemical sensors 10 having different chemical
substance capturing portions 5 described above are connected to a
detection system 12 via a selection switch 13 are included. In the
modified example of Example 4, a plurality of types of
predetermined chemical substances 6 can be simultaneously measured
including the spatial distribution by the m number of detection
systems 12-1 to 12-m.
[0114] In the chemical sensor of the invention, since the distance
between the first electrode and the second electrode for detecting
the change in the dielectric constant is configured to have a value
smaller than the predetermined ratio (approximately 100 times) with
respect to the size of the molecule of the predetermined chemical
substance to be detected, it is possible to detect a change in the
dielectric constant between the facing electrodes without requiring
signal amplification.
[0115] Hereinbefore, although the invention made by the inventor is
specifically described based on the embodiments, it is needless to
say that the invention is not limited to the embodiments described
above, and various modifications can be made without departing from
the gist thereof.
* * * * *